Numerous devices exist in the prior art for controlling the flow of fluid. A subclass of such devices includes fluid flow control systems. Fluid flow control systems regulate the rate of distribution of transport fluid through a line. Some examples of fluid control systems are kidney dialysis machines and intravenous blood transfusion devices. Fluid flow control system may include a cassette holder in which a disposable cassette is placed and wherein transport fluid is pumped by a membrane which is part of the cassette.
FIG. 1 shows a portion of a prior art flow control system 14 which includes a cassette 10 mounted on a cassette holder 12. A flexible membrane 11 covers the face of the flow control system cassette 10 and is permanently attached to the cassette 10.
The flow control system 14 has a valving chamber 17 located in the cassette and a valve control volume 19 located in the cassette holder 12 which defines a valve 50. A portion of the flexible membrane 11 separates the valving chamber 17 and the valve control volume 19 and acts as a barrier to keep control fluid in the valve control volume 19 from mixing and contaminating transport fluid in the valving chamber 17. The control fluid is delivered to the valve control chamber 19 through a valve control fluid line 15.
The flow control system 14 has a pump chamber 18 located in the flow control system cassette 10 and a pump control volume 100 located in the cassette housing 12 which defines a pump 52. A portion of the flexible membrane 11 separates the pump chamber 18 and the pump control volume 100 and acts as a barrier to keep the control fluid in the pump control chamber 100 from mixing and contaminating the transport fluid in the pump chamber 18 while transport fluid is being pumped into or out of the pump chamber 18. The control fluid is delivered to the pump control chamber 100 through a pump control fluid line 16.
One problem with such a system is the cassette membrane may become punctured during transportation and handling of the cassette. If pinholes develop in the cassette membrane, the transport fluid may leak into the cassette holder requiring the cassette holder to be cleaned and replaced. Additionally, the control fluid may contaminate the transport fluid. The prior art system described above did not determine if there is a leak in the cassette after it is mounted in the cassette holder and prior to any transport fluid being pumped through the cassette.